The RoboFont docs have some good advice for working with big fonts.
This repo contains a few scripts which are slightly adapted for a workflow to work with many masters at once.
Run open-fonts-in-SimpleFontWindow.py to select UFOs to open in simple font windows. These don't contain thumbnail previews of glyphs, and that speeds up editing significantly. This also opens up glyph A in all fonts, to make it easy to use editThatNextMaster.
The regular "Save All" function doesn't always work with simple font windows, so you can use save-allfonts-in-simplefontwindows.py to save all fonts at once.
Run layersShowhideHotkey.py to activate a hotkey h, which will show/hide background layers in all fonts. Currently, you need to run this each time you restart RoboFont, but that may change in the future.
- Install the RoboFont extension editThatNextMaster so you can cycle through glyphs easily.